[tex]P_{kwadrat} =P_{\Delta niebieski} +P_{figury~~zacienionej} +P_{\Delta czerwony}\\\\P_{figury~~zacienionej} = P_{kwadrat} - P_{\Delta niebieski} - P_{\Delta czerwony}\\\\P_{kwadrat} = b^{2} \\\\P_{\Delta niebieski} =\dfrac{1}{2} \cdot (b-1)\cdot (b-2)=\dfrac{1}{2} \cdot (b^{2} -2b-b+2)= \dfrac{1}{2} \cdot(b^{2} -3b+2)=\dfrac{1}{2} b^{2} -1\dfrac{1}{2} b+1\\\\ P_{\Delta czerwony}=\dfrac{1}{2}\cdot b\cdot b= \dfrac{1}{2}b^{2} \\\\Podstawiam:\\\\[/tex]
[tex]P_{figury~~zacienionej} =b^{2} -( \dfrac{1}{2}b^{2})-(\dfrac{1}{2} b^{2} -1\dfrac{1}{2} b+1)\\\\P_{figury~~zacienionej} =b^{2} -\dfrac{1}{2}b^{2}-\dfrac{1}{2} b^{2} +1\dfrac{1}{2} b-1\\\\P_{figury~~zacienionej} =b^{2} -b^{2} +1\dfrac{1}{2} b-1\\\\P_{figury~~zacienionej} =1\dfrac{1}{2} b-1[/tex]
